Farmers in South Texas looking for a good rotation crop that provides ample residue for conservation-tillage can’t do better than grain sorghum. “Grain sorghum is the queen of residue, and does well along the Texas Gulf Coast,” says Texas A&M Extension agronomist Steve Livingston.
Livingston discussed the value of grain sorghum in a reduced-tillage rotation system during the recent Conservation Tillage, Cotton and Rice Conference in Houston. The big question, he says, is whether grain sorghum can be profitable. That depends a lot on yield potential, he says, and yield can vary significantly with planting date.
Late planting, generally, reduces yield potential. “If we knew what the weather was going to do, selecting a planting date would be easy.”
Livingston says in years with normal temperatures, a planting date 10 days on either side of Feb. 22 is best. “In three years of planting date studies with as many as eleven planting dates spaced one week apart, during wet growing seasons sorghum loses (approximately) 38 pounds for each day of delay after February 22. “In dry seasons, where little or no rain falls following planting, sorghum loses 69 pounds per day of delay after February 22.”
He says short season sorghum outperforms medium or long-season varieties in a dry year. But in wet years, the long-season hybrids “often provide the most grain.”
Grain sorghum’s highest water needs begin at peak bloom, about 45 days after planting. During that time, one inch of rainfall may increase yield potential by 450 to 700 pounds “if received in adequate amounts.”
He says a 4.5-inch rain accumulation within one week of boot stage initiation increased yields dramatically. Well-drained soils produce better yields, although in wet years sandy, marginal land might outperform heavy, black clay and clay loam soils because of drainage.
Grain sorghum also works well with conservation tillage systems. Livingston says typical South Texas land preparation includes shredding stalks, chiseling and disking. “We lose a lot of residue and lose a lot of surface cover that ends up in the ditch,” he says.
He says if farmers decide to shred grain sorghum stalks they should still spray ratoon growth and emerged weeds just before cold weather. “In a good production year, grain sorghum can provide more than 75 percent ground cover for subsequent crops.”
He says a trash master and knockdown bars may be necessary to manage residue before planting the next crop. “Trash masters or other type finger-wheels to set aside surface residue permit the planter to place seed accurately,” Livingston says. “The covering fingers replace the residue over the planted furrow.”
Livingston says a rain following planting is ideal to “facilitate germination and to seal trenches left by injected fertilizer application.”
He says corn or cotton does well as conservation tillage crops behind grain sorghum. Livingston says pre-conditioning grain sorghum for harvest improves harvest efficiency and also reduces weed seed production and subsequent weed problems in following crops. He says a glyphosate material works well as a harvest pre-conditioner.
He also says leaving the stalks standing through winter provides excellent cover throughout corn and cotton growing season. Stalks are knocked down at planting time.
Standing stalks prevent loose residue from washing off fields in heavy rain. “Knives used in liquid fertilizer application help align old stalks and break up soil near the planting furrow,” he says.
Hybrid selection also affects yield potential and Livingston says growers have a number of good options. “We have better hybrids,” he says. “Those with improved stay-green commonly yield better in growing seasons with late-season drought stress. These are more difficult to pre-condition for harvest and may not die immediately with lower rates of glyphosate.”
Stay-green hybrids include DKS-52, DKS-54 and Pioneer 84G. Lower residue sorghums with thinner canopies and stalks include A571, DKS 45 or NC+ 7R83. “Growers often use from 13 ounces to 16 ounces of WeatherMax to precondition these hybrids. An application at 22 ounces or a second rate of 11 ounces of WeatherMax might be necessary to kill high stay-green hybrids.”
He says the stay-green hybrids “buy from three to seven days for the grain sorghum. It stays green longer and feeds the kernels.” Lower residue hybrids with less stay-green may not yield as well in some growing seasons, he says.
Livingston says corn may be more successful in the Gulf Coast area four of eight years. But grain sorghum is more reliable. “Corn is more profitable if we get 26 inches of rain.” He says grain sorghum has no aflatoxin issues and that markets in nearby Mexico improve profit potential.